In the operation of a multi-color rotary offset printing press, freshly printed substrates such as sheets or web material may be guided by various cylinders from one printing unit to another, and then they are delivered to a sheet stacker or to a sheet folder/cutter unit, respectively. The cylinders are known by various names including transfer cylinders, delivery cylinders, transfer rollers, support rollers, delivery wheels, skeleton wheels, segmented wheels, transfer drums, support drums, spider wheels, support wheels, guide wheels, guide rollers, etc.
The cylinders may be installed in and removed from printing presses at various times and for various reasons. Printing presses are often built and delivered without transfer and/or delivery cylinders. Such cylinders are normally installed before operating the presses. However, printing presses often have structural cross members, such as tie bars, which must be removed to provide sufficient space to install a cylinder. Removal and replacement of the cross members takes a considerable amount of time and may require the services of a professional press mechanic. Once installed, a transfer cylinder often blocks access to a back cylinder, e.g. an impression cylinder, which needs to be cleaned or maintained on a regular basis, for example daily. While various special cleaning devices have been devised to reach around or over a transfer cylinder to clean the back cylinders, cleaning is much easier if the transfer cylinder is removed. Various types of printing jobs may require transfer cylinders of different diameters. But, as noted above, removal and/or replacement of a cylinder often requires removal and replacement of cross members.